Amiga 1000 - Page 30

BASIC
OPERATING
THEORY
COMMODORE-AMIGA
1000 SYSTEM
— ^
When
the
Copoer
is
Halted it is
off
the
Data
3us
and
doesn't
use
any
Cvcles until
the
Wait is
over. A
Programmed
Wait Value
is
compared to
the 3e^r.
Ccunter,
which
keeps
track
of
the
TV
beam
position.
When
these
2
values
are
ecual,
the
Copper
resumes fetching
instructions.
"
The
Copper' can
cause
Interrupts,
reload the
Color
Registers, start the
Blittar
or
service'
the
Audio. The
Copper can
modify
almost
any Resister
in the Custom
SLIDE
7
—
BLITTER DMA
The Blitter
uses
4 DMA Channels, 3
Sources and 1
Destination.
Once
the Blitter
has
been
started these
4 DMA
Channels
are
synchronized
and
pipelined
to
automatically
handle the Data
Transfers
without further 63000 MPU Intervention.
The
Images are
manipulated
in
memory independent of the
display.
(3itplane
DMA)
With
the three
sources A, B,
and
C
along
with their
inverses, they
combine in
eight
ways for a
possible
256 Combinations.
SLIDE
8
—
DENISE
BLOCK
The 8362 DENISE
is the
Display
Encoder Chip. The Internal
Circuitry of DENISE
is
comprised
of
approximently 19,000 Transistors.
The main
function
is to Buffer
Display Data, Select the object to
be displayed
at
any
instant
and
encode the
object
into Red,
3lue and Green Color
Codes.
The
Bitplane Data
is
continuously
loaded
and
serialized
during
the Display
Time.
The
Sprite
Data
is
loaded
during
Blank -Time
and
serialized
individually
whenever the
Sprite
Position
Ccmpare Logic
detects
equality
between the Sync
Counter
and any
Sprite
Position
Register.
The 6
lines
of
Bit
Plane
Serial
Data
and
the
8
pairs
of
Sprite
Serial Data
feed
into
the
Priority
Control
Logic
which selects
only
one of
the
Sprites
or
one
of the Separate
Bitmap
Images
to
produce
the 5
Bit
Color Select
Code
at the
output.
This 5 Bit
Code
selects one of the
32 Color
Registers
producing
the
12
Bit RGB,
(Red,
Green,
Blue),
Video Output.
>
The 6 lines
of Bit
Plane
Serial Data
and
the 8
pairs
of Sprite
Serial
Data
also
feed
into
the
Collision
Detect
Logic which
detects Real
Time
Occurance
between them and
sets
the
appropriate bits
in the
Collision
Storage
Register. The
68000 MPU
Reads
and
Clears this
register.
The 2
Mouse/Joystick
Connectors
are
controlled
by 4
Mouse
Counters.
The
Mouse
Counters
count
the
Horizontal
and
Vertical
Motion of
the
Controllers.
These
counters
are
read
by the
68000 MPU.
SLIDE
9
—
BITPLANE
DMA
The
Bitplane
uses
6 DMA
Channels. During
display the
Bitplane
_
Controller
continuously
transfers
Display
Data from
memory
to
Display
Buffer
Registers.
The
6
DMA Channels
handle
the
data from 6
Independent
Bitp
lanes. The
Display
Buffers
convert
this Bitplane
Data
into
Pixel
Data
for
the
display.
Each
Bitplane
can be a
full
image,
or a window
into an
image
that
is
up
to
4
times
the
screen
size. They can
be
grouped
into 2
separata
imagc-s,
each
with
its
own
Color
Registers.